Apparatus for image transfer with charged particle beam, and deflector and mask used with such apparatus

ABSTRACT

A image transferring apparatus using a charged particle beam including a projection lens for transferring a pattern formed on a mask onto a target by focusing a charged particle beam passing through the mask, and a deflector for deflecting the charged particle beam passing through the mask toward a predetermined direction (x-axis direction) so that a transfer position of the pattern to the target is changed. In this apparatus, the deflector includes a deflection coil for generating a deflection magnetic field extending in a direction (y-axis direction) perpendicular to the predetermined direction, and correction coils for generating correction magnetic fields extending in the same direction as the deflection magnetic field at areas spaced apart from the center of the deflection magnetic field along the direction (x-axis direction) perpendicular to the direction of the deflection magnetic field.

This is a divisional of application Ser. No. 08/548,616 filed Oct. 26,1995, now U.S. Pat. No. 5,689,117.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a deflector for deflecting a chargedparticle beam toward a desired position, and more particularly, itrelates to a deflector suitable for use with a transferring apparatusfor transferring a mask pattern onto a photosensitive substrate by usinga charged particle beam. The present invention also relates to a chargedparticle beam transferring apparatus for transferring a pattern imageformed on a mask onto a target object by using a charged particle beam.

2. Description of the Related Art

As one of lithographic apparatuses for printing an integrated circuit ona semiconductor wafer, there has been proposed a charged particle beamreduction-transferring apparatus wherein a charged particle beam isdirected onto a mask is used having a predetermined pattern and apattern included in an illumination range is reduction-transferred ontoa wafer through a projection lens. In such an apparatus, a mask is usedon which a number of small regions each having the pattern are borderedin a grid pattern by bordering regions having no pattern (for example,refer to U.S. Pat. No. 5,260,151). Thus, the electron beam passingthrough the small region on the mask must be deflected by an amountcorresponding to a width of the bordering region by means of a deflectorso that the pattern images of the small regions are positionedcontiguous to each other when they are transferred onto the wafer. Sucha deflector includes deflection coils such as coils 1a, 1b ofsaddle-type, as shown in FIG. 6A, or toroidal coils 2a, 2b, as shown inFIG. 6B. The saddle coils 1a, 1b are wound to define a pair of curvedsurfaces positioned symmetrically with respect to a center-line CL ofthe deflector so that a magnetic field H extending perpendicular to thecenter-line CL is generated by applying currents flowing in thedirections shown by the arrows. The toroidal coils 2a, 2b are wound on acylindrical core ring 2c symmetrically with respect to a center line CLof the core ring so that a magnetic field H extending perpendicular tothe center-line CL of the core ring 2c is generated by applying currentsflowing in the directions shown by the arrows.

In the above-mentioned conventional transferring apparatus, ifdeflection sensitivity of the deflector is not uniform in across-section of the electron beam, deflection distortion will occur inthe transferred pattern. In the conventional deflectors, the deflectionsensitivity is greatly changed in accordance with positions in themagnetic field, and, since a range in which the uniform deflectionsensitivity can be obtained is limited to a very small area near thecenter of the deflector, it is necessary to utilize a deflector having adimension considerably greater than the field dimension of the mask. Forexample, when it is assumed that a permissible value for the deflectiondistortion of the electron beam passing through the small region (on themask) having a dimension of 1 mm×1 mm after the beam is deflected by 1mm on the wafer is 10 nm, permissible accuracy cannot be obtained unlessthe electron beam passes through a narrow area within D/8-D/10 from thecenter-line CL of the deflector where D is an inner diameter of the coreof the deflector (inner diameter of a ferromagnetic cylinder contactedwith an outer side of a deflection coil; refer to FIG. 2). The followingcalculation results show examples of a relationship between a ratio(core inner diameter of deflection coil/maximum field dimension of mask)and the deflection distortion. Incidentally, in each of these examples,the calculated value represents an amount of the deflection distortionwhen the small region (on the mask) having the dimensions of 1 mm×1 mmis deflected by 1 mm on the wafer with pattern reduction of 1/4 (fromthe mask to the wafer).

(1) When the ratio is:

core inner diameter/maximum field dimension=1.14:

    0.518×(1/5.7)×(1/4)=22.7 μm

(2) When the ratio is:

core inner diameter/maximum field dimension=1.6:

    0.137×(1/8)×(1/4)=4.28 μm

(3) When the ratio is:

core inner diameter/maximum field dimension=2.0:

    0.0574×(1/10)×(1/4)=1.43 μm

(4) When the ratio is:

core inner diameter/maximum field dimension=2.6:

    0.019×(1/13.3)×(1/4)=356 nm

(5) When the ratio is:

core inner diameter/maximum field dimension=4:

    4.02×10.sup.-3 ×(1/20)×(1/4)=50.25 nm

(6) When the ratio is:

core inner diameter/maximum field dimension=8:

    2.56×10.sup.-4 ×(1/40)×(1/4)=1.6 nm

As is apparent from the above calculation results, there arises aproblem that the deflection distortion cannot be sufficiently reducedunless the inner diameter of the core of the deflector is set to becomefive to eight times greater than the maximum field dimension of themask.

On the other hand, in the conventional charged-particlebeam-transferring apparatuses, it has been accepted that, when adistance between the mask and the target is L, the reduction ratio ofthe pattern from the mask to the target is 1/n and a point spaced apartfrom the mask toward the target by an amount of L·n/(n+1) is set as a"cross-over" of the charged particle beam (for example, an electronbeam), low aberration can be obtained when a position bisecting adistance between the mask and the cross-over coincides with a centralposition of the projection lens at the mask side and a positionbisecting a distance between the cross-over and the target coincideswith a central position of the projection lens at the target side. Onthe other hand, Japanese Patent Laid-open No. 5-160012 (1993) disclosesa technique in which the mask side projection lens is displaced from thelens position toward the mask by an amount of ε (ε is a positiveconstant) and the target side projection lens is displaced from the lensposition toward the target by an amount of n·ε.

In the charged particle beam reduction-transferring apparatuses, if theelectron beam emitted from an electronic gun has energy divergence,radial and azimuthal aberrations (transverse chromatic aberration) willtake place. The transverse chromatic aberration includes a real numberportion representing radial aberration and an imaginary number portionrepresenting azimuthal aberration. These transverse chromaticaberrations are substantially proportional to the cube of the magnitudeof a visual field of an optical system. The transverse chromaticaberration cannot be corrected by so-called "field division" wherein themain visual field of the optical system is divided into a plurality ofsub-fields and the pattern is division-transferred by transferring therespective sub-field, successively. Accordingly, the transversechromatic aberration causes problems, particularly when the main visualfield of the optical system is great. In this specification, the fieldbefore the field division is called a "main visual field" and each ofthe divided small areas is called as "sub-field".

In the above-mentioned conventional apparatuses, when it is assumed thatthe point internally dividing the distance between the mask and thetarget with reduction ratio is set as the cross-over, theoretically, amain light beam of the electron beam incident on the mask perpendicularthereto passes through the cross-over. However, since the projectionlens has spherical aberration, if a lens condition is determined tosatisfy the positive focus condition in each sub-field, the main lightbeam of the electron beam incident on the mask perpendicular theretowill not necessarily pass through the cross-over, thereby generatingdistortion. To avoid such distortion, the lens condition must beselected so that the main light beam of the electron beam passes throughthe cross-over (In this case, the main light beam incident on the maskis not perpendicular to the mask). Similarly, regarding the positionbetween the cross-over and the target, the lens condition for satisfyingthe perpendicularity of the electron beam to the target does notcoincide with the lens condition for passing the electron beam throughthe cross-over. Accordingly, in order to reduce the distortion of thepattern, the perpendicularity of the electron beam to the target shouldbe given up. However, when the incident direction of the electron beamis inclined with respect to a plane perpendicular to a transfer surfaceof the target to which the pattern is to be transferred, if the transfersurface is deviated along an optical axis of the optical system due to awarp of the target, the transfer position of the pattern will also bedeviated, thereby causing pattern error is caused.

When the mask including a number of small regions having the patternsand bordered in the grid pattern by the bordering regions is used, theelectron beams passing through the mask are deflected so that thepattern regions are contiguous to each other without interposing anybordering regions in the transferred area on the target (such as awafer). Since the deflection amount is increased as the number of thesmall regions is increased, when the semiconductor having a largesurface area is manufactured, a large deflector must be used, therebymaking the optical system bulky and thus increasing the distortion ofthe transferred pattern.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a deflector and acharged particle beam transferring apparatus using such a deflector, inwhich a greater range in the deflector can be used for performingdeflection.

To achieve the above object, according to the present invention, thereis provided a charged particle beam transferring apparatus comprising adeflection coil means for generating a deflection magnetic field todeflect a charged particle beam, and a correction coil means forgenerating a correction magnetic field to correct deflection sensitivityof the deflection coil.

The present invention further provides a charged particle beamtransferring apparatus comprising a projection lens means fortransferring a pattern formed on a mask onto a target by gatheringcharged particle beams passing through the mask, and a deflector meansfor deflecting the charged particle beams passing through the masktoward a predetermined direction (x-axis direction) to change transferpositions of segments of the pattern, wherein the deflector meansincludes a deflection coil means for generating a deflection magneticfield extending in a direction (y-axis direction) perpendicular to thepredetermined direction, and a correction coil means for generatingcorrection magnetic fields extending in the same direction as thedeflection magnetic field at areas spaced apart from the center of thedeflection magnetic field along a direction (x-axis direction)perpendicular to the direction of the deflection magnetic field.

Another object of the present invention is to provide a charged particlebeam reduction-transferring apparatus which can reduce transversechromatic aberration regarding radial and azimuthal aberrations.

To achieve this object, according to the present invention, there isprovided a charged particle beam reduction-transferring apparatus forreduction-transferring a pattern image of a mask onto a target bydirecting an electron beam passed through the mask to first and secondprojection lenses successively, wherein, when a distance between themask and the target is L, reduction ratio of the pattern from the maskto the target is 1/n, a positive constant number is ε and a point spacedapart from the mask toward the target by an amount of L·n/(n+1) is setas a cross-over of the charged particle beam optical system, the centralposition of the first projection lens along an optical axis thereof isdisplaced toward the cross-over by an amount of n·ε with respect to theposition bisecting the distance between the mask and the cross-over, andthe central position of the second projection lens along an optical axisthereof is displaced toward the cross-over by an amount of ε withrespect to the position bisecting the distance between the cross-overand the target.

The present invention further provides a charged particle beamreduction-transferring apparatus for reduction-transferring a patternimage of a mask onto a target by directing an electron beam passedthrough the mask to first and second projection lenses successively,wherein the bore radii R_(1c), R_(2c) of the first and second projectionlenses on the cross-over side are set to be smaller than 1/4 of the boreradii R_(1o), R_(2o) on the other side.

A further object of the present invention is to provide a chargedparticle beam transferring apparatus wherein both a condition regardingperpendicularity of an electron beam incident on a mask and a target anda condition for passing a main light path of the electron beam throughthe cross-over are satisfied simultaneously.

To achieve this object, according to the present invention, there isprovided a charged particle beam transferring apparatus for transferringa pattern image of a mask onto a target by using a charged particlebeam, comprising an angle adjusting deflector means for adjusting anincident angle of the charged particle beam incident on the mask or thetarget.

A still further object of the present invention is to provide a chargedparticle beam transferring mask and a charged particle beam transferringmethod, wherein a deflection amount of a charged particle beam passingthrough the mask can be reduced or the deflection of the chargedparticle beam can be eliminated.

To achieve this object, according to the present invention, there isprovided a charged particle beam transferring mask wherein a pattern tobe transferred to a target is divided into a plurality of patternsegments which are formed on a plurality of corresponding small regionsdisposed side-by-side in vertical and horizontal directions, and thesmall regions are bordered by bordering regions each having no pattern,and further wherein the pattern segments to be transferred to the targetin a line are divided and formed on first and second rows of smallregions.

The present invention further provides a charged particle beamtransferring method wherein a mask (in which a pattern to be transferredto a target is divided into a plurality of pattern segments which areformed on a plurality of corresponding small regions disposedside-by-side in vertical and horizontal directions and the small regionsare bordered by bordering regions each having no pattern) is used and acharged particle beam is successively directed on the small regionsdisposed side-by-side along a second direction (Y-axis direction)perpendicular to a first direction (x-axis direction) while shifting themask and the target in the first direction along which the small regionsare disposed side-by-side, thereby performing the transferring of thepattern, and further wherein, after the transferring of one row or aplurality of rows of small regions disposed side-by-side along thesecond direction is finished and before the transferring of an adjacentrow of small regions in the first direction is started, a shifting speedof the mask in the first direction is made greater than a shifting speedof the target in the first direction so that a relative distance betweenthe mask and the target is changed by an amount equal to or a pluralityof times a width of the bordering region in the first direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration showing an optical system between amask and a wafer in a charged particle beam transferring apparatusaccording to a first embodiment of the present invention;

FIG. 2 is a sectional view taken along the line II--II in FIG. 1;

FIG. 3 is a perspective view schematically showing a deflection coil anda correction coil according to the first embodiment;

FIGS. 4A and 4B are views showing a relation between a position of thecorrection coil and magnetic field intensity of a deflector;

FIG. 5 is a perspective view showing a transferring operation of thecharged particle beam transferring apparatus according to the firstembodiment;

FIG. 6A is a perspective view of saddle-type coils of the deflector, andFIG. 6B is a perspective view of toroidal coils of the deflector;

FIG. 7 is a schematic illustration showing a symmetrical magneticdoublet optical system of a charged particle beam reduction-transferringapparatus according to a second embodiment of the present invention;

FIG. 8 is a graph showing a relation between a distance ΔL (between theposition bisecting the distance between the cross-over and a target, anda center-line position of a second projection lens at the target side)and azimuthal chromatic aberration Δφ;

FIG. 9 is a graph showing a relation between a ratio of the bore radiusR_(bc) of the projection lens at the cross-over side to the bore radiusR_(bo) at the other side and the transverse chromatic aberration Δφ;

FIG. 10 is a schematic illustration showing a transferring apparatusaccording to a third embodiment of the present invention;

FIG. 11 is an enlarged view of the projection lens and therearound;

FIG. 12 is a view showing a principle of angular adjustment in theapparatus according to the third embodiment of the present invention;

FIG. 13 is a view for explaining a procedure for seeking inclination θof a beam;

FIGS. 14(a) and 14(b) are schematic illustrations showing a relationbetween the mask and wafer during the transferring operation in theapparatus of FIG. 10;

FIGS. 15A and 15B are views showing various kinds of masks;

FIG. 16 is a flow chart showing a control sequence of a control devicewhen the transferring operation is effected in a manner shown in FIG.14;

FIG. 17 is a view showing an example that an incident angle is adjustedby means of a single deflector;

FIGS. 18(a) and 18(b) are views showing a relation between the mask andthe wafer according to a fourth embodiment in the present invention,where FIG. 18(a) is a partial plan view of the mask and FIG. 18(b) is apartial plan view of the wafer;

FIG. 19 is a schematic illustration showing an electron beamreduction-transferring apparatus in a fifth embodiment of the presentinvention;

FIG. 20 is a flow chart showing a control sequence for shifting a maskstage and a wafer stage carried out by means of a control device of FIG.19; and

FIG. 21 is a graph showing a relation between a time elapsed after thetransferring is started in the sequence of FIG. 20 and a shiftingdistance of a mask image projected on the wafer and a shifting distanceof the wafer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will be explained withreference to FIGS. 1 to 5. FIG. 1 schematically shows an optical systembetween a mask and a wafer in a charged particle beam transferringapparatus according to the first embodiment. In FIG. 1, the apparatusincludes a mask 10, a first projection lens 11, a second projection lens12, and a wafer 13 comprised of a photosensitive substrate acting as atarget. Within a magnetic pole (core) 110 of the first projection lens11 at the mask side, there are disposed a deflection coil means 14 and acorrection coil means 15, which will be fully described later. Above themask 10, there are disposed an electronic gun for emitting an electronbeam, a condenser and an aperture for forming the electron beam as abeam having a rectangular cross-section (square in the illustratedembodiment), and a visual field selecting deflector for directing theformed electron beam to a predetermined position on the mask 10;however, these elements are omitted from illustration. The mask 10 andthe wafer 13 can be shifted, by means of respective stages (not shown)in an x-axis direction (perpendicular to the plane of FIG. 1) and ay-axis direction which are orthogonal to each other in a planeperpendicular to an optical axis AX of the optical system. Hereinafter,a direction along the optical axis AX is referred to as a z-axisdirection.

FIG. 5 shows a condition in which the operation is performed by usingthe above-mentioned transferring apparatus. In FIG. 5, the directions ofthe X-axis, y-axis and z-axis are the same as those shown in FIG. 1. Thelenses and the deflection coil means are omitted from illustration inFIG. 5. As apparent from FIG. 5, the mask 10 has a plurality ofrectangular small regions 10a, and bordering regions 10b dividing orbordering the small regions in a grid pattern. The pattern to betransferred to an area 13a (corresponding to one chip, i.e., onesemi-conductor) on the wafer 13 is divided into pattern segments, andthese pattern segments are formed on the corresponding small regions10a. The electron beam EB emitted from the electronic gun (not shown) isformed to have a square cross-section slightly greater than the smallregion 10a, and is deflected by means of the visual field selectingdeflectors (not shown) from the optical axis AX of the optical systemtoward the x-axis direction so that it is directed to one of the smallregions 10a on the mask 10. The bordering regions have no pattern, andthe electron beam directed to the bordering region does not reach thewafer 13. Incidentally, the details of the pattern segment formed oneach small region 10a is not illustrated. A cross-over point of theelectron beam EB provided by the projection lens 11 is designated by"CO".

In the above-mentioned apparatus, during the transferring operation, forexample, as shown by the arrows Fm, Fw, the mask 10 and the wafer 13 arecontinuously shifted in opposite directions along the y-axis direction.Synchronously with these continuous movements, the electron beam EBdirected to the mask 10 is scanned step-by-step in the x-axis directionby a pitch of the small region 10a so that the small regions 10adisposed side by side along the x-axis direction are successivelyilluminated by the electron beam EB. As a result, the pattern segmentsformed on the small regions 10a are transferred, by means of theprojection lenses 11, 12, onto predetermined areas 13b on the wafer 13with a predetermined reduction ratio (for example, 1/4). One of thepredetermined area 13b on the wafer 13 corresponds to one of the smallregions 10a on the mask 10.

Upon transferring the pattern image, the electron beam EB passingthrough the mask 10 is deflected by magnetic fields generated by thedeflection coil means 14 and the correction coil means 15 in the x-axisdirection by an amount corresponding to the width of the borderingregion 10b. That is to say, since a non-exposed area corresponding tothe bordering region 10b of the mask 10 is formed between the adjacentexposed areas 13b on the wafer if the electron beams EB passing throughthe corresponding small regions 10a are merely focused on the wafer 13by the first and second projection lenses 11, 12, the transfer positionfor each pattern segment is displaced in the x-axis direction by theamount corresponding to the width of the bordering region 10b so thatthe transferred images of the pattern segments are contiguous with eachother. After the transferring of the pattern segments on a row of smallregions 10a disposed side-by-side along the x-axis direction iscompleted, the transferring of the pattern segments on a next row ofsmall regions adjacent to the previous row in the y-axis direction isperformed. By repeating similar operations, the pattern segments formedon all of the small regions 10a of the mask 10 are transferred onto thewafer 13.

As mentioned above, in the transferring apparatus according to the firstembodiment, since the electron beam passed through the mask 10 isdeflected merely in the x-axis direction, the visual field orfield-of-view of the optical system has an elongated rectangular shapeincluding a row of small regions 10a disposed side-by-side along thex-axis direction and corresponding bordering regions 10b. That is tosay, as shown by the reference numeral 20 in FIG. 2, an area throughwhich the electron beam passes in the magnetic pole 110 of theprojection lens 11 has a rectangular shape elongated in the x-axisdirection, and the electron beam does not pass through any areasurrounding the elongated rectangular area (visual field) 20.Accordingly, a zone between an area 21 including the visual field 20with some play or margin and the inner boundary of the magnetic pole 110can be used as a space for installing the deflection coil. Further, itis important that the deflection sensitivity is uniform within thevisual field 20 in FIG. 2, and the deflection sensitivity regarding thearea surrounding the visual field does not affect the deflectiondistortion of the images transferred to the wafer 13. Thus, in theillustrated embodiment, the deflection coil means 14 and the correctioncoil means 15 are installed as follows.

As shown in FIGS. 2 and 3, the deflection coil means 14 comprises a pairof saddle-type coils wound in close contact with the inner surface ofthe magnetic pole 110. Accordingly, the magnetic pole 110 is used as acore for the deflection coils 14. The direction of the magnetic fieldgenerated by the deflection coils 14 is shown by the arrows H1 and isorthogonal to the visual field 20. A wide angle 2θ of the deflectioncoil 14 with respect to a central position CP of the magnetic pole 110(coincides with the optical axis AX) is 120 degrees, because, when thewide angle is 120 degrees, the third term of the deflection magneticfield becomes zero. The intensity of the magnetic field generated bysuch deflection coils 14 is decreased at peripheral portions spacedapart from the center CP of the magnetic field in the direction (x-axisdirection) perpendicular to the direction of the magnetic field. Thus,in the illustrated embodiment, the correction coil means 15 are disposedin the vicinity of both longitudinal ends of the visual field 20 togenerate correction magnetic fields H2 each having the same direction asthe deflection magnetic field. Each correction coil is wound in a saddlefashion, as shown in FIG. 3.

By providing the deflection coil means 15 and the correction coil means15 in this way, in the vicinity of the both ends of the visual field 20,the magnetic fields H2 of the correction coil means 15 are overlappedwith the deflection magnetic field to compensate for the reduction ofthe intensity of the magnetic field of the deflection coil means 14.Accordingly, by adjusting values of currents applied to the correctioncoil means 15, it is possible to improve the deflection sensitivity ateach end of the visual field 20 to become substantially the same as thedeflection sensitivity at the central portion of the visual field,thereby suppressing the deflection distortion. In this case, since themagnetic flux flown out of the correction coil means 15 is returned tothe correction coil means again through the magnetic core 110, themagnetic field at the central portion of the deflector is not negativelyinfluenced.

Considering one-fourth of the cross-section of the magnetic pole 110, asshown in FIG. 4A, the test data regarding the change (along the x-axisdirection) in the field intensity Hy in this cross-section with respectto the x-axis direction and the change ratio (dHy/dx) of the fieldintensity are shown in FIG. 4B. Here, the x-axis direction and they-axis direction are the same as those shown in FIGS. 1 and 2. Theabscissa in the graph shown in FIG. 4B has a unit scale corresponding toone-eight of the radius of the magnetic pole 110. A half-angle θ of thewide angle of the deflection coil is 60 degrees. For comparison's sake,the test data in the case of no correction coil 15 are also shown. As isapparent from the graph, in the case of no correction coil, the fieldintensity begins to decrease from a position slightly spaced apart fromthe center of the deflector. To the contrary, when the correction coils15 are provided and the currents applied thereto are properly adjusted,the field intensity can be maintained substantially uniformly from thecenter to the vicinity of both ends of the visual field. Morespecifically, when the visual field 20 at the mask side has rectangulardimensions of 80 mm×1 mm and an area 21 is defined to have margins of 10mm in both longitudinal and widthwise directions of the visual field andwhen the positions x_(h), Y_(h) and the coil widths Δx, Δy of thecorrection coils are selected to be 5, 1 and, 0.5, 0,1, respectively,and the number of windings of each correction coil is the same as thatof the deflection coil 14 and further when the current applied to eachcorrection coil 15 is greater than that of each deflection coil 14 by1.3 times, it was found that the change ratio of the deflectionsensitivity can be suppressed to 3% or less per one-eight of the innerradius of the magnetic pole within a range between 0/8 and 6/8 of theinner radius of the magnetic pole 110.

In the illustrated embodiment, while the deflection coil means 14 is ofa saddle-type, each deflection coil may comprise a toroidal coil. Insuch a case, it is necessary to form holes or slits in the magnetic pole110 through which the windings of the coil are passed. Further, thepositions of the correction coils 15 are not limited to those shown inFIGS. 1 and 2, but the correction coils may be disposed at positionswhere the deflection sensitivity should be corrected.

As mentioned above, in the illustrated embodiment, since the change inthe deflection sensitivity can be suppressed by overlapping thecorrection magnetic fields generated by the correction coil means withthe deflection magnetic field generated by the deflection coil means,even if the wider space (range) in the deflection coil means than theconventional techniques is used for the deflection purpose, it ispossible to limit the deflection distortion within a predeterminedrange. Thus, the deflector can be made more compact. Particularly, incharged particle beam transferring apparatuses using the deflectoraccording to the present invention, since the deflector can be disposedwithin the magnetic pole of the projection lens efficiently and the boreradius of the lens magnetic pole can be decreased, the incident angle ofthe charged particle beam to the photosensitive substrate can approachninety degrees, thereby improving the transferring accuracy.

More specifically, since the magnetic pole 110 nearest to the mask 10has an inner diameter greater than those of the other magnetic poles,the deflection coil means 14 and the correction coil means 15 can bedisposed efficiently in the available space within the magnetic pole110. Since the inner diameter of the deflection coil means 14 can bedecreased, there is no need to increase the bore radius of the magneticpole 110 for installation of the deflection coil means 14. Accordingly,it is possible to reduce the influence of the magnetic field generatedby the magnetic pole 110 on the incident angle of the charged particlebeam, thereby causing the incident angle of the charged particle beamincident on the mask to approach 90 degrees.

Next, a second embodiment of the present invention will be explainedwith reference to FIGS. 7 to 9.

FIG. 7 shows a symmetrical magnetic doublet optical system of a chargedparticle beam reduction-transferring apparatus according to a secondembodiment of the present invention. The apparatus includes a mask 201,a first electromagnetic projection lens 202, a second electromagneticprojection lens 203, and a target 204. The reference numeral 205 denotesa cross-over point. Above the mask 201, there are disposed an electronicgun, a condenser and a visual field selecting deflector, which are notshown. With this arrangement, an electron beam is selectively directedonto one of a plurality of sub-fields (small-regions) formed on the mask201. The electron beam passing through the mask 201 is focused on thecross-over 205 by means of the first projection lens 202, and theelectron beam diverging from the cross-over is focused on the target 204by means of the second projection lens 203. Consequently, the patternimage of the sub-field on the mask 201 is transferred onto the target204 with a predetermined reduction ratio of 1/n. Although the reductionratio 1/n can be determined appropriately, in the illustratedembodiment, the reduction ratio is selected to be 1/4. In FIG. 7, anoptical axis of the optical system is designated by "AX".

The cross-over 205 is a position (point) obtained by internally dividinga distance between the mask 201 and the target 204 with the reductionratio of 1/n. That is to say, when the distance between the mask 201 andthe target 204 is L and a distance between the mask 201 and thecross-over 205 is S, the following relation (1) is established:

    S=L·n/(n+1)                                       (1)

As mentioned above, in the illustrated embodiment, since n=4, thedistance S becomes 4L/5(i.e. S=4L/5).

FIGS. 8 is a graph showing a relation between a distance ΔL (thedistance between a position bisecting the distance between thecross-over and the target, and a center line position of the secondprojection lens, i.e., projection lens at the target side) and azimuthalchromatic aberration Δφ, which was calculated by the inventors of thepresent invention. The abscissa in the graph indicates the distance ΔL(a direction that the second projection lens approaches the target is"positive" and a direction that the second projection lens leaves thetarget is "negative"). In FIG. 8, the solid line φ2 represents thechromatic aberration regarding paraxial path calculated on the basis ofthe distribution of the magnetic field of the lens in the optical axisdirection and its first differentiation. That is to say, the solid lineφ2 indicates a value obtained by seeking an aberration coefficient onthe basis of deviation of the path at an image point when beam energy isslightly changed in the paraxial path and by multiplying the aberrationcoefficient by magnitude of the visual field. As can be seen from thegraph, if it is assumed that the entire electron beam is in the paraxialpath, when ΔL=2 mm (i.e., when the center-line position of the secondprojection lens is shifted toward the target by 2 mm from the positionbisecting the distance between the cross-over and the target), theaberration can be minimized. Accordingly, regarding the first projectionlens, the center-line position of the first projection lens may beshifted toward the mask by an amount of 2n (obtained by multiplying thereciprocal n of the reduction ratio 1/n) form the position bisecting thedistance between the mask and the cross-over.

However, since the electron beam directed to a peripheral portion of thevisual field (particularly, a main visual field when field-division iseffected) in the electron beam reduction-transferring apparatus isgreatly spaced apart from the optical axis of the electron beam opticalsystem, it cannot be assumed that the electron beam is in the paraxialpath. Thus, by calculating the chromatic aberration on the basis of theactual path of the electron beam, the result shown by the solid line φ1in FIG. 8 was obtained. As is apparent from this result, in the electronbeam reduction-transferring apparatus, the chromatic aberration isdecreased as the central position of the second projection lensapproaches from the position bisecting the distance between thecross-over and the target toward the cross-over. Accordingly, when thecentral position of the first projection lens approaches toward thecross-over from the position bisecting the distance between the mask andthe cross-over, the chromatic aberration can also be decreased. And,when the second projection lens is shifted toward the cross-over by anamount of ε(>0), by shifting the first projection lens toward thecross-over by an amount of n·ε (where the pattern reduction ratio is 1/nbetween the mask and the target), the chromatic aberration can bereduced.

Next, when the inventors of the present invention calculated a relationbetween the ratio R_(bc) /R_(bo) (between the bore radius R_(bc) of theprojection lens at the cross-over side and the bore radius R_(bo) at theother side) and the chromatic aberration Δφ, the result shown by thesolid line φ3 in FIG. 9 was obtained. From this result, it was foundthat the chromatic aberration can be minimized by setting the boreradius R_(bc) at the cross-over side to be less than one-fourth of thebore radius R_(bo) at the other side. By satisfying the aboverequirements, the chromatic aberration can be reduced. Since the radialaberration is less than 1/2-1/3 of the azimuthal aberration Δφand ischanged in the same manner as the change in the chromatic aberrationshown in FIGS. 8 and 9, the above-mentioned results regarding theazimuthal aberration can be applied to the radial aberration.

According to the above requirements, in the example shown in FIG. 7, thecenter-line position M1 of the first projection lens 202 (positionbisecting the distance between the magnetic poles 202a and 202b) isdisplaced from the position HH1 bisecting the distance between the mask201 and the cross-over 205 toward the cross-over 205, and thecenter-line position M2 of the second projection lens 203 (positionbisecting the distance between the magnetic poles 203a and 203b) isdisplaced from the position HH2 bisecting the distance between thecross-over 205 and the target 204 toward the cross-over 205. When adisplacement amount of the second projection lens 203 is ε (>0), adisplacement amount of the first projection lens 202 is set to thereciprocal multiple of the reduction ratio 1/4 (i.e., 4ε). The boreradius R_(1c) of the magnetic pole 202b (at the cross-over 205 side) ofthe first projection lens 202 is set to one-fourth of the bore radiusR_(1o) of the magnetic pole 202a at the other side, and the bore radiusR_(2c) of the magnetic pole 203a (at the cross-over 205 side) of thesecond projection lens 203 is set to one-fourth of the bore radiusR_(2o) of the magnetic pole 203b at the other side.

With this arrangement, when ε=8 mm, R_(1c) =20 mm, R_(1o) =80 mm, R_(2c)=5 mm and R_(2o) =20 mm and when the dimension of the main visual fieldon the target 204 is set to 20 mm×20 mm, from the calculation result ofthe chromatic aberration, it was ascertained that the azimuthalaberration can be reduced below 2 nm/eV. Further, even when thedivergence of energy emitted from the electronic gun is 5 eV, it wasfound that the deterioration of beam resolving power due to theazimuthal chromatic aberration can be suppressed below 10 nm. Therefore,according to the illustrated embodiment, the pattern of thesemiconductor element having a width of the shorter side of 20 mm orless can be transferred accurately without interconnecting the mainvisual fields.

As mentioned above, according to the present invention, the radial andazimuthal chromatic aberrations can be adequately reduced by installingthe first and second projection lenses at optimal positions along theoptical axis in consideration of the actual path of the electron beamand by appropriately selecting the bore radii of these projectionlenses. Accordingly, even when the energy of the electron beam emittedfrom the electronic gun has divergence, the deterioration of the beamresolving power can be suppressed, with the result that the transferringcan be performed with high through-put by enlarging the visual field ofthe optical system while maintaining the transferring accuracy. Further,any electronic gun for emitting an electron beam having a relativelylarge energy width can be used without considering a problem regardingchromatic aberrations.

Next, a third embodiment of the present invention will be explained withreference to FIGS. 10 to 17.

FIG. 10 schematically shows an electron beam reduction-transferringapparatus according to the third embodiment of the present invention,which comprises an electronic gun 301, a condenser lens 302 forcollimating an electron beam emitted from the electronic gun 301, atwo-stage visual field selecting deflector means 303a, 303b fordirecting the electron beam EB passing through the condenser lens 302 toa predetermined position on a mask 304, a mask stage 305 for holding themask 304, a two-stage transfer position correcting deflector means 306a,306b for deflecting the electron beam passing through the mask 304 by apredetermined amount, a first projection lens 307, a second projectionlens 308, and a wafer stage 309 on which a wafer 310 is mounted. Themask 304 will be fully described later. The mask stage 305 can beshifted in an x-axis direction (direction perpendicular to the plane ofFIG. 10) and a y-axis direction. The wafer stage 309 can be shiftedhorizontally in the x-axis direction and the y-axis direction and canalso be lifted and lowered in a z-axis direction. The z-axis directioncoincides with a direction parallel to optical axes AX of the first andsecond projection lenses 307, 308, and the x-axis direction and they-axis direction are orthogonal to each other in a plane perpendicularto the z-axis direction. An x-axis direction, a y-axis direction and az-axis direction shown in FIGS. 11 to 14 are determined in the samemanner as in FIG. 10.

The above-mentioned arrangement is included in the conventionaltransferring apparatus. The transferring apparatus according to thisthird embodiment has the following characteristic arrangement. That isto say, in the illustrated embodiment, two-stage angle adjustingdeflector means 311a, 311b are disposed above the mask 304 and two-stageangle adjusting deflector means 312a, 312b are disposed below the mask,and two-stage angle adjusting deflector means 313a, 313b are disposed infront of the wafer stage 309. Although these sets of deflector means311a, 311b, 312a, 312b, 313a, 313b serve to deflect the electron beam inthe y-axis direction, other sets of similar deflector means (not shown)are also provided to deflect the electron beam in the x-axis direction.The reason for the provision of two sets of deflector means will bedescribed later. By the above deflector means 311a, 311b, 312a, 312b,313a, 313b, an angle of the electron beam is adjusted to simultaneouslysatisfy a condition that the electron beam incident on the mask 304 andthe wafer 310 becomes perpendicular to the latter and a condition that amain light beam of the electron beam passing through the firstprojection lens 307 passes through the cross-over CO. The details willbe described later.

The deflection sensitivity of each of the deflector means 311a, 311b,312a, 312b, 313a, 313b is independently controlled by means of a controldevice 320 via interfaces 321, 322, 323. The control device 320 servesto control the entire operation of the transferring apparatus, and, morespecifically, it controls the deflection sensitivity of each angleadjusting deflector means. It also controls setting conditions of theelectronic gun 301, condenser lens 302, first projection lens 307 andsecond projection lens 308, as well as the deflector means 303a, 303band 306a, 306b via interfaces 324, 325, respectively, and also controlsoperations of actuators 326, 327 for the mask stage 305 and the waferstage 309. The position of the mask stage 305 in the x-axis and y-axisdirections and the position of the wafer stage 309 in the x-axis, y-axisand z-axis directions are detected by position detectors 328, 329,respectively, and the detected information is sent to the control device320. The reference numeral 330 denotes an input device for inputtingvarious data such as a transferring condition to the control device 320;and 331 denotes a memory.

FIG. 11 schematically shows the optical system between the mask 304 andthe wafer 310. However, the deflector means 306a, 306b shown in FIG. 10are omitted from illustration in FIG. 11. Coils of the angle adjustingdeflector means 312a, 312b are disposed on an inner peripheral surfaceof a magnetic pole 307a (at the mask side) of the first projection lens307, and coils of the angle adjusting deflector means 313a, 313b aredisposed on an inner peripheral surface of a magnetic pole 308a (at thewafer side) of the second projection lens 308. When the distance betweenthe mask 304 and the wafer 310 is L and the reduction ratio of thepattern from the mask 304 to the wafer 310 is 1/n, the distance La fromthe mask 304 to the cross-over CO of the first projection lens 307becomes L·n/(n+1), and the distance Lb from the cross-over CO to thewafer 310 becomes L/(n+1).

When the distance between the magnetic poles 307a and 307b of the firstprojection lens 307 is Lc and the distance between the magnetic pole307a and the mask 304 is Ld, the distortion generated during thetransferring of the pattern is reduced as the distance Lc is increasedand the magnetic field of the lens leaking toward the mask side isreduced as the distance Ld is increased, thereby improving theperpendicularity of the electron beam incident on the mask. That is tosay, if the electron beam is incident on the mask 304 perpendicularthereto and angular adjustment (described later) is not effected by thedeflector means 312a, 312b, a deviation amount between a position wherethe main light beam of the electron beam passed through the firstprojection lens 307 intersects with the optical axis AX and thecross-over CO is reduced as the distance Ld is increased. However, sincethe distance L is naturally limited due to the limited dimension of alens barrel of the optical system and the distance La between the mask304 and the cross-over CO is also limited, as the distance Ld isincreased the distance Lc is decreased accordingly, with the result thatthe distortion cannot be improved. Regarding the second projection lens308, the same problem occurs as understood when considering anarrangement where the mask 304 is replaced by the wafer 310. Thus, inthe illustrated embodiment, the angle of the electron beam is adjustedby the above-mentioned deflector means 311a, 311b, 312a, 312b, 313a,313b in accordance with the principle shown in FIG. 12.

In FIG. 12, the broken line PR1 represents the main light beam of theelectron beam if the angle adjustment is not effected by the deflectormeans 311a, 311b, 312a, 312b, and the solid line PR2 represents the mainlight beam of the electron beam when the angle adjustment is effected bythe deflector means 311a, 311b, 312a, 312b. The distance "a" between themask 304 and the deflector 311b is the same as the distance "a" betweenthe mask and the deflector 312a, and the distance "b" between thedeflector 311b and the deflector 311a is the same as the distance "b"between the deflector 312a and the deflector 312b. At the downstreamside of the center position P2 of the deflector 312b in the optical axisdirection, the main light beam PR1 and the main light beam PR2 passthrough the cross-over CO through the same path.

As is apparent from FIG. 12, if the angle adjustment according to theillustrated embodiment is not effected, the main light beam PR1 passingthrough the visual field selecting deflector means 303a, 303b will beincident on the mask 304 in a condition that it is inclined by an angleθ with respect to the z-axis direction (parallel with the optical axisAX) toward a direction spaced away from the optical axis AX. To thecontrary, in the illustrated embodiment, the main light beam PR2 isfirst deflected outwardly by an angle θ2 by means of the uppermostdeflector 311a and then is deflected inwardly by an angle θ1 by means ofthe next deflector 311b so that the main light beam PR2 is incident onthe mask 304 perpendicular thereto. In this case, the incident positionof the main light beam PR2 to the mask 304 coincides with the incidentposition P1 of the main light beam PR1. Then, the main light beam PR2passed through the mask 304 is deflected outwardly by the angle θ1 bymeans of the deflector 312a so that the main light beam passes throughthe center position P2 of the deflector 312b at the same point throughwhich the beam PR1 passes. Thereafter, the main light beam PR2 isdeflected inwardly by the angle θ2 so that the main light beam PR2 canpath along the same path as the main light beam PR1. In this case, thestarting point of the main light beam PR2 to be deflected by thedeflectors 312a, 312b is the point P1 on the mask 304.

Regarding the wafer 310, an arrangement obtained when FIG. 12 is turnedupside down and the first projection lens 307 and the mask 304 arereplaced by the second projection lens 308 and the wafer 310,respectively, may be considered. The corresponding reference numerals incase of this imaginary arrangement are indicated in the parentheses. Atthe wafer 310 side, since the main light beam passing through the secondprojection lens 308 is inclined by the angle θ with respect to thez-axis direction toward a direction approaching the optical axis AX, themain light beam is first deflected inwardly by the angle θ2 by means ofthe deflector 313a and then is deflected outwardly at the angle θ1 sothat the incident angle of the beam to the wafer 310 is 90 degrees. Inthis case, the incident position of the main light beam to the wafer 10can coincide with the incident position obtained if the angle adjustmentis not effected.

Next, a method for setting the deflection sensitivity when the angleadjustment is effected will be explained.

As is apparent from FIG. 12, the following equations (1) and (2) can beestablished:

    θ1=θ2+θ                                  (1)

    (a+b)·θ=θ1·b                 (2)

By solving the above simultaneous equations (1), (2) to remove or delete"θ", the following equation (3) can be obtained:

    (a+b)·(θ1-θ2)=θ1·b

Therefore,

    θ2/θ1=a/(a+b)                                  (3)

From the above, the deflection sensitivity of each of the deflectors311a, 311b, 312a, 312b can be set to have a ratio shown by the equation(3). However, as is apparent from FIG. 12, θ1 and θ2 have oppositesigns.

In the equation (3), θ1 and θ2 (and θ) are unknown quantities. Now, amethod for seeking these values θ1, θ2 will now be explained.

First of all, from the equation (2), the following equation (4) can bederived:

    θ1=((a+b)/b)·θ                        (4)

From the equations (4) and (3), the θ2 can be determined as follows:

    θ2=((a+b)/b)·(a/(a+b))·θ=a·θ/b(5)

Thus, when the value of θ is determined, the values θ1, θ2 can becalculated.

The angle θ is actually measured as the incident angle of the main lightbeam incident on the wafer. For example, the measurement is performed asshown in FIG. 13. First of all, a test piece TP having a crisscrossmarker CM formed thereon is rested on the wafer stage 309 (FIG. 10).Then, while the route or path of the electron beam is being keptconstant, the test piece TP is shifted in the x-axis and y-axisdirections between two positions spaced apart from each other by anamount of Δz in the z-axis direction. Meanwhile, positions where thecenters, O₂, O₂ of crisscross of the marker CM coincide with the mainlight beam PR are determined by detecting electrons reflected from thetest piece TP. The coordinates (x₁, y₁, z₁), (x₂, y₂, z₂) of the centersO₁, O₂ are determined from the position of the wafer stage 309, and theinclination θ of the main light beam can be calculated on the basis ofdifferences Δx, Δy, Δz in coordinates. Incidentally, a crisscross markerCM' shown by the two-dot chain line in FIG. 13 represents a case wherethe inclination θ of the main light beam is zero. If the main light beamPR passes through the cross-over CO as is in the main light beam PR1 ofFIG. 12, the inclination θ provides a condition that the aberration isminimized when the incident position of the main light beam PR incidentto the wafer 310 is positioned at the center O₁ or O₂.

In the example shown in FIG. 13, the main light beam PR is inclined byan angle φ with respect to the x-axis direction. On the other hand, asmentioned above, the angle adjustment effected by the deflectors islimited to the X-axis and Y-axis directions. Thus, in order to determinethe actual deflection sensitivity, the inclination θ is divided intoinclination (Δx/Δz) in the x-axis direction and inclination (Δy/Δz) inthe y-axis direction, and inclination values θ obtained for x-axis andy-axis are entered into the above equations (4) and (5). In this way,the perpendicularity of the electron beam in the rotational directionand the perpendicularity of the electron beam in the radial directioncan be satisfied simultaneously.

In this way, the deflection sensitivity of each of the deflectors 311a,311b, 312a, 312b, 313a, 313b (when the perpendicular incident conditionof the electron beam to the mask 304 and the wafer 310 and the conditionthat the main light beam passes through the cross-over aresimultaneously satisfied) is determined in correspondence to theincident position of the electron beam to the wafer 310. The obtainedrelations between respective deflection sensitivity and the incidentposition are previously stored in the memory 331 of FIG. 10. Since theoptimum value of the deflection sensitivity is varied with the incidentposition of the electron beam to the wafer 310, the deflectionsensitivity is previously determined regarding all of the incidentpositions during the actual transferring operating.

Next, a transferring sequence effected by the transferring apparatusaccording to the illustrated embodiment will be described. FIGS. 14(a)and 14(b) schematically show a relation between the mask 304 and thewafer 310 during the transferring. In FIGS. 14(a) and 14(b), the lensesand deflectors are omitted from illustration. As apparent from FIG.14(a), the mask 304 has a plurality of rectangular small regions 304a,and bordering regions 304b bordering the small regions in a gridpattern. A pattern (the details of which is not illustrated) to betransferred to an area 310a (corresponding to one chip, i.e., onesemiconductor) (referred to as "chip area" hereinafter) on the wafer 310is divided into pattern segments, and these pattern segments are formedon the corresponding small regions 304a. The electron beam transferringmask may be formed by disposing scattering elements SC capable ofscattering the electron beam at a large scattering angle on a thin filmMB having high permeability to the electron beam to form the pattern, asshown in FIG. 15A, or may be formed by forming openings OP correspondingto the pattern in a substrate BP blocking the electron beam, as shown inFIG. 15B. In the illustrated embodiment, either of the mask of FIG. 15Aor 15B can be used. In any cases, the bordering regions 304b areuniformly formed from the material capable of blocking the electron beamor greatly scattering the electron beam. The configuration of the wafer310 is as shown in FIG. 14(b), and a portion (a portion Va in FIG.14(b)) of the wafer 310 is shown in FIG. 14(a) with an enlarged scale.

The electron beam EB emitted from the electronic gun 301 of FIG. 10 isformed to have a square cross-section slightly greater than the smallregion 304a, and is deflected by means of the visual field selectingdeflectors 303a, 303b by a predetermined amount so that it is directedto one of the small regions 304a on the mask 304. The pattern segmentformed on each small region 304a is reduction-transferred onto a unitarea 310b within the chip area 310a on the wafer 310 through theprojection lenses 307, 308 of FIG. 10. That is to say, in theillustrated embodiment, the small region 304a corresponds to thesub-field at the mask side, and the unit area 310b corresponds to thesub-field at the wafer side. The selection of the small region 304a iseffected in the following manner.

During the transferring operation, as shown by the arrows Fm, Fw, themask 304 and the wafer 310 are continuously shifted in oppositedirections along the x-axis direction. When a given row of small regions304a disposed side-by-side along the y-axis direction reaches thetransferring start position, by these continuous movements, the electronbeam EB is scanned step by step in the y-axis direction by a pitch inthe row of the small regions 304a so that the small regions 304adisposed side-by-side along the y-axis direction are successivelyilluminated by the electron beam EB. Synchronously with the scanning ofthe electron beam, the electron beam EB is deflected in the y-axisdirection by means of the deflectors 306a, 306b of FIG. 10 by an amountcorresponding to the width (in the y-axis direction) of the borderingregion 304b, with the result that the pattern images formed on the rowof small regions 304a disposed side-by-side along the y-axis directionare successively transferred onto the wafer 310 along the y-axisdirection. After the transferring of the pattern images on the row ofthe small regions 304a is finished, when a next row of small regions304a adjacent to the previous row in the x-axis direction reaches thetransferring start position, the transferring of the next row isstarted. In this way, the pattern images formed on all of the smallregions 304a of the mask 304 are transferred to the chip area 310a ofthe wafer 310.

FIG. 16 is a flow chart showing a control sequence of the control device320 when the pattern is transferred to the whole area on the wafer. Whenthe wafer 310 is mounted on the wafer stage 309 and the transferringstart command is inputted, the control device 320 selects the chip area310a to which the pattern images are to be transferred (step S1) and thewafer stage 309 is driven so that the selected area 310a is brought to apredetermined position. Then, in a step S2, the mask 304 and the wafer310 are continuously shifted by the mask stage 305 and the wafer stage309. In the next step S3, the sub-field, i.e., the small region 304a tobe illuminated by the electron beam is selected. The order of selectionof the area 310a and the small region 304a is previously inputted fromthe input device 330 to the control device 320.

After the sub-field is selected, the sequence goes to a step S4, wherethe optical conditions are set in accordance with the sub-field. Theoptical conditions include operating conditions of the lenses 307, 308and the deflectors 303a, 303b, 306a, 306b, operating conditions of theangle adjusting deflectors 311a, 311b, 312a, 312b, 313a, 313b and thelike. That is to say, when the small region 304a from which the patternis to be transferred is determined, since the position of thecorresponding area 310b on the wafer 310 can also be determined, thedeflection sensitivity corresponding to this position is derived fromthe memory 331 and such deflection sensitivity is set. After the opticalconditions are set, the sequence goes to a step S5, where thetransferring is started. After the transferring of one small region 304ais finished, the sequence goes to a step S6, where it is judged whetheror not the transferring of one chip area 310a is finished. If not, thesequence is returned to the step S3, where a next region to betransferred is selected among non-transferred regions. On the otherhand, if affirmative, the sequence goes to a step S7, where it is judgedwhether or not the transferring of all of the chip areas 310a on thewafer 310 is finished. If not, the sequence is returned to the step S1,where the non-transferred chip area is selected as the transfer area. Onthe other hand, if affirmative, the sequence is ended.

As mentioned above, in the illustrated embodiment, since regarding allof the sub-fields, the condition as to the perpendicularity of theelectron beam incident to the mask 304 and the wafer 310 and thecondition that the main light beam passes through the cross-over areboth satisfied, even if the mask 304 and/or the wafer 310 is displacedin the z-axis direction due to the warp and the like, the pattern errordoes not occur and the pattern can always be transferred with minimumdistortion. Even when the magnetic poles 307a, 308a of the projectionlenses 307, 308 are disposed near the mask 304 and the wafer 310, sincethe perpendicularity of the beam incident to the mask and the wafer canbe ensured, the lenses 307, 308 themselves can be designed with lowaberration. Since the angular adjustment is effected by means of thetwo-stage deflector means 312a, 312b at the mask 304 side and thetwo-stage deflector means 313a, 313b at the wafer 310 side withutilizing the positions of the mask 304 and the wafer 310 as thedeflection centers, the incident position of the electron beam is notchanged between the times before and after the angle adjustment isperformed. That is to say, as shown in FIG. 17, if the electron beamincident on the mask is deflected only by the single stage deflector312b to pass through the cross-over CO, since the incident position P1of the electron beam to the mask 304 before the angle adjustment isdeviated from the incident position P1' of the electron beam to the maskafter the angle adjustment by an amount α, it is necessary to correctthe incident position by shifting the mask 304 in the deflecteddirection by the amount α, thereby reducing the through-put accordingly.However, if the deviation α of the incident position can be correctedfor a short time, the single stage deflector may be used.

Incidentally, when the mask having the thin film support structure asshown in FIG. 15A is used and when the thin film MB is formed frommono-crystal material and the crystal orientation providing the longestmean free path is aligned with the direction of the optical axis AX, bycombining such a mask and the illustrated embodiment, the scattering ofthe charged particle beam passing through the thin film MB can besuppressed to the minimum extent.

As mentioned above, according to the present invention, by deflectingthe charged particle beam by means of the angle adjusting deflectormeans, since the beam path (course) can be adjusted to the desiredcondition at the mask side and the target side while maintaining thecondition that the main light beam of the charged particle beam passesthrough the cross-over, the condition regarding the perpendicularity ofthe charged particle beam incident to the mask and the target and thecondition that the main light beam of the charged particle beam passesthrough the cross-over can be satisfied simultaneously, therebyeffecting the transferring with high accuracy. Further, in theillustrated embodiments, the above-mentioned two conditions can besatisfied simultaneously regarding all of the sub-fields, the incidentposition of the charged particle beam to the mask and the target can bekept constant before and after the adjustment of the beam orbit, and theperpendicularity of the charged particle beam incident on the mask andthe target in the radial direction and the perpendicularity in thecircumferential direction can be adjusted regarding all of thesub-fields.

When the transferring is performed by using the mask shown in FIG.14(a), if the pattern segments formed on a row of small regions 304adisposed side-by-side along the y-axis direction are merely projected onthe wafer 310 through the pair of projection lenses, gaps eachcorresponding to the bordering region 304b will be generated between thetransfer areas 310b (corresponding to the small regions 304a) on thewafer 310. To avoid this, it is necessary to deflect the electron beamEB passed through each small region 304a in the y-axis direction by anamount corresponding to the width Ly of the bordering region 304a tocorrect the pattern transfer position. Also regarding the x-axisdirection, if the mask 304 and the wafer 310 are merely shifted at aconstant speed depending upon the reduction ratio of the pattern, afterthe transferring of one row of small regions 304a is finished, when thenext row of small regions 304a are transferred, it is necessary todeflect the electron beam EB passed through the small region in thex-axis direction by an amount corresponding to the width Lx of thebordering region 304b to prevent gaps (in the x-axis direction) fromgenerating between the transfer areas 310b. However, when the electronbeam passing through the mask 304 is deflected to correct the patterntransfer position on the wafer 310 as mentioned above, the maximumdeflection amounts in the x-axis and y-axis directions are increased asthe number of the small regions 304a is increased. Accordingly, whenthis deflecting technique is used with a lithographic apparatus forhandling a semiconductor having a large surface area, a considerablylarge-sized deflector must be used, thereby making the optical systembulky. In addition, since the deflection amount is increased, thepattern distortion during the transferring is also increased, therebyworsening the transferring accuracy.

When the transferring operation as mentioned above is performed, theorder for scanning the small regions 304a and the order for transferringthe pattern segments onto the wafer 310 are as shown by the arrows A andB in FIG. 14(a).

Next, a fourth embodiment of the present invention which can prevent theincrease in deflection amount will be explained with reference to FIGS.18(a) and 18(b). FIGS. 18(a) and 18(b) show a relationship between amask and a wafer according to the fourth embodiment, where FIG. 18(a) isa partial plan view of the mask 600 and FIG. 18(b) is a partial planview of the wafer 610. An x-axis direction and a y-axis direction arethe same as those shown in FIG. 14(a). The mask 600 has a plurality ofrectangular small regions 600a on each of which a pattern segmentdivided from a pattern (to be transferred) is formed, and borderingregions 600b bordering the small regions in a grid pattern and eachhaving no pattern. In this mask 600, in the y-axis direction, a width Wyof the small region 600a is the same as a width Ly of the borderingregion 600b. Further, regarding the y-axis direction, the small regions600a in first rows R1 are aligned with the bordering regions 600binadjacent second rows R2 or vice versa. A width Lx (in the x-axisdirection) of the bordering region 600b is the same as that of FIG.14(a).

In the mask 600, the pattern segments to be transferred onto the wafer610 in one line along the y-axis direction are formed on the smallregions 600a in each of the first and second rows R1, R2. And, arelation between the small regions 600a in one of the first rows R1 andthe small regions 600a in the corresponding adjacent second row R2, andtransfer areas 610b on the wafer 610 is selected such that all of thesmall regions 600a in the first row R1 and the second row R2 aretransferred to the all of the transfer areas 610b in a single row whilemaintaining the positions of the small regions 600a in the y-axisdirection unchanged. For example, when it is assumed that the patternsegment of the small region 600a₁ in the first row R1 is transferredonto the transfer area 610b₁, the pattern segment of the small region600a₂ in the second row R2 is transferred onto the adjacent transferarea 610b₂, and the pattern segment of the small region 600a₃ in thesame first row R1 is transferred onto the next transfer area 610b₃.Similarly, the small regions 600a in the first and second rows R1, R2are transferred onto the row of transfer areas 610b on the wafer 610alternately. During the transferring operation, first of all, the smallregion 600a in the first row R1 is scanned by the electron beam, andthen, the small region 600a in the second row R2 is scanned by theelectron beam. In this case, in order to transfer the pattern segmentson the small regions in the first and second rows R1, R2 onto thetransfer areas 610b on the wafer 610 in a line, the electron beamspassed through the small regions 600a are appropriately deflected in thex-axis direction.

According to the above-mentioned mask 600, for example, since the smallregion 600a₁, in the first row R1 is adjacent to the small region 600a₂in the second row R2 regarding the y-axis direction, when the patternsegments on these small regions are transferred onto the transfer areas610b₁, 610b₂, respectively, there is no need to deflect the electronbeams in the y-axis direction. Accordingly, even when a large number ofsmall regions 600a are disposed along the y-axis direction, thetransferring operation can be performed with high accuracy. Thus, thereis no need for using a deflector having a large dimension in the y-axisdirection, thereby making the optical system compact. In theabove-mentioned mask 304 of FIG. 14, since the widths (in the y-axisdirection) of the bordering regions 304b is small, great heatdeformation of the bordering regions 304b may be caused due to theheating of the regions by illumination with the electron beam. However,in the mask 600 according to this embodiment, since the borderingregions 600b each has a greater dimension, the heat can easily dissipatefrom these regions, thereby suppressing the heat deformation. If thewidth Ly of the bordering region 600b is greater than the width Wy ofthe small region 600a, so long as the difference (Ly-Wy) is smaller thanthe width of the bordering region 304b of FIG. 14(a), the deflectionamount (in the y-axis direction) of the electron beam can be reduced incomparison with the example shown in FIG. 14(a).

Next, a fifth embodiment of the present invention will be explained withreference to FIGS. 19 to 21. This embodiment utilizes the mask 304 shownin FIG. 14(a), and, thus, a detailed explanation of the mask 304 and thewafer 510 will be omitted. FIG. 19 shows an electron beamreduction-transferring apparatus used in this embodiment, whichcomprises an electronic gun 401, a condenser lens 402 for collimating anelectron beam emitted from the electronic gun 401, a visual fieldselecting deflector means 403 for directing the electron beam passedthrough the condenser lens 402 to a predetermined small region 304 onthe mask 304, a mask stage 404 for translating the mask 304 in thex-axis and y-axis directions, an actuator 405 for the mask stage 404, adeflector means 406 for deflecting the electron beam passed through themask 304 in the y-axis direction, a deflector means 407 for deflectingthe electron beam in the x-axis direction, a first projection lens 408,a second projection lens 409, a wafer stage 410 for translating thewafer 510 in the x-axis and y-axis directions, and an actuator 411 forthe wafer stage 410.

The positions of the mask stage 404 and the wafer stage 410 in thex-axis and y-axis directions are detected by position detectors 412, 413such as laser interferometers, and the detected results are sent to acontrol device 414. The control device 414 controls the deflector means403, 406, 407 via interfaces 415, 416 so that the pattern segments onthe mask 340 are transferred onto the wafer 510 in the same manner asdescribed in connection with FIG. 14(a) and also controls the operationsof the actuators 405, 411. Regarding the mask of FIG. 14(a), althoughthe mask 304 and the wafer 310 are shifted at a constant speed in thex-axis direction, in the fifth embodiment, the shifting movements of themask 304 and the wafer 510 are controlled in accordance with thesequence shown in FIG. 20.

After the positioning of the mask 304 and the wafer 510 and thepreparation required for effecting the transferring have been finished,when the transferring start command is inputted, first of all, in a stepS11, the control device 414 starts to shift the mask stage 44 and thewafer stage 410 in the x-axis direction. The ratio between the shiftingspeed of the mask stage 404 and the shifting speed of the wafer stage410 is equal to the reduction ratio of the pattern. Synchronously withthe initiation of the shifting movements of the stages, a row (in they-axis direction) of small regions 304a on the mask 304 are scanned bythe electron beam step by step. In this case, the illuminating positionof the electron beam is adjusted by the visual field selecting deflectormeans 403. After the stages are started to be continuously shifted, thesequence goes to a step S12, where it is judged whether or not thetransferring the row of small regions 304a is completed. If affirmative,the sequence goes to a step S13; otherwise, the similar judgement isrepeated.

In the step S13, it is judged whether or not the transferring of allof-rows of small regions 304a is finished or not. If not, the sequencegoes to a step S14, where the wafer stage 410 is temporarily stopped. Ina next step S15, it is judged whether a predetermined waiting timeperiod ti is elapsed by means of a counter (not shown) incorporated inthe control device 414. The waiting time period ti is a time periodrequired for shifting the mask 304 by an amount corresponding to thewidth Lx (in the x-axis direction) of the bordering region 304b. If thewaiting time period is has not elapsed, a similar judgement is repeated.On the other hand, if the waiting time period has elapsed, the sequencegoes to a step S16, where the shifting movement of the wafer stage 410in the x-axis direction is re-started. In synchronous with the re-startof the shifting movement, a next row of small regions 304a is scanned bythe electron beam. In the step S13, if affirmative, the sequence goes toa step S17, where the mask stage 404 and the wafer stage 410 arereturned to their initial positions for preparation for nexttransferring, and then, the sequence is ended. When the pattern of themask is continuously transferred onto a plurality of chip areas 510a onthe wafer 510, the above-mentioned sequence is repeated. In the abovesequence, the judgements in the steps S12 and S13 can be performed bydetermining the shifted distances of the mask stage 404 and the waferstage 410 from the transfer start point (in the x-axis direction) on thebasis of the detected results of the position detectors 412, 413. Sincethe time period required for scanning one row and the time periodrequired for scanning all of the rows can be previously known, thejudgements in the steps S12 and S13 may also be performed on the basisof the elapsed time period.

FIG. 21 is a graph showing a relationship between an elapsed time periodfrom the transfer start time and each of a shift distance of an image(mask image) obtained by projecting the mask 304 onto the wafer 510 anda shift distance of the wafer itself, when the sequence of FIG. 20 iscarried out. The dot and chain line S1 represents the shift distance ofthe mask image and the solid line S2 represents the shift distance ofthe wafer 510. A difference ΔS between the shift distance of the maskimage and the shift distance of the wafer indicates the deviation of therelative position between the mask 304 and the wafer 510. In the abovesequence, since the mask stage 404 is shifted at a constant speed in thex-axis direction, the shift distance of the mask image is continuouslyincreased from the transfer start point at given inclination orgradient. Although the wafer 510 is shifted in a completely synchronousrelationship with the mask image till a time t1 when the transferring ofthe row of small regions 304a on the mask 304 is finished after thetransferring is started, the wafer is stopped from the time t1 (when onerow transfer is finished) to a time t2 when the transferring of the nextrow is started; meanwhile, the waiting time period ti is elapsed. Due tothis stoppage, there arises the deviation in the relative positionbetween the mask 304 and the wafer 510. However, since the mask 304 isshifted by an amount corresponding to the width Lx of the borderingregion 304b within the waiting time period ti, at the time t2, a row ofsmall regions 304a on the mask 304 to be newly transferred is alignedwith a row of transfer areas 510b on the wafer 510 in the x-axisdirection, with the result that there is no need to deflect the electronbeam passed through the mask 304 in the x-axis direction.

Similarly, since the wafer 510 is temporarily stopped at times t3, t5,t7, . . . tm (m is odd) when the transferring of each row of the smallregions 304a on the mask 304 is finished and the shifting movement ofthe wafer 510 is at times t4, t6, t8, . . . tn (n is even) after themask 304 is shifted by the amount corresponding to the width Lx of thebordering region 304b, there is no need to deflect the electron beampassed through the mask 304 in the x-axis direction by an amountcorresponding to the width Lx of the bordering region 304b. Accordingly,regarding the deflector means 407 (FIG. 19), if the error in positions(in the x-axis direction) of the mask 304 and the wafer 510 is causeddue to the error of shifting movements of the mask 304 and the wafer510, the electron beam may be deflected merely to correct such error,with the result that the deflection amount of the electron beam is verysmall. The deflection amount actually supposed is on the order of ±1 μm.

In the above-mentioned embodiments, the x-axis direction corresponds tothe first direction and the y-axis direction corresponds to the seconddirection. In the illustrated embodiment, while an example that therelative position between the mask 304 and the wafer 510 is changed in acondition that the wafer stage 410 is stopped is explained, between thetime t1 and the time t2 in FIG. 21, the wafer stage 410 may beaccelerated or the mask stage 404 may be decelerated. In such a case,the deflection amount (in the x-axis direction) of the electron beam canbe reduced by an amount corresponding to the increase in the relativeshifting movement of the mask 304. This adjustment is not necessarilyeffected whenever the transferring of each row of small regions isperformed, but may be effected, for example, every five rows if apermissible deflection amount in the x-axis direction is greater thanthe width Lx by five times.

What is claimed is:
 1. A charged particle beam deflector comprising:adeflection coil for generating a deflection magnetic field capable ofdeflecting a charged particle beam; and a correction coil for generatinga correction magnetic field capable of correcting deflection sensitivitydistribution of said deflection coil.
 2. A charged particle beamdeflector according to claim 1, wherein said correction coil generatessaid correction magnetic field so that the deflection sensitivity ofsaid deflection magnetic field is increased at a peripheral portion ofsaid deflection magnetic field.
 3. A charged particle beam deflectorcomprising:a deflection coil for generating a deflection magnetic fieldcapable of deflecting a charged particle beam; and a correction coil forgenerating a local correction magnetic field directed in the samedirection as said deflection magnetic field within said deflectionmagnetic field.
 4. A charged particle beam deflector according to claim3, wherein said correction coil is disposed so that said correctionmagnetic fields are generated in areas spaced apart from a center ofsaid deflection magnetic filed along a direction perpendicular to thedirection of said deflection magnetic filed.
 5. An image transferringapparatus using a charged particle beam comprising:a projection lens fortransferring a pattern formed on a mask onto a target by focusing acharged particle beam passed through said mask at the target; and adeflector for deflecting the charged particle beam passed through saidmask in a predetermined direction so that a transfer position of thepattern on said target is changed, said deflector comprising adeflection coil for generating a deflection magnetic field extending ina direction perpendicular to said predetermined direction, and acorrection coil for generating a correction magnetic field extending inthe same direction as said deflection magnetic field at an area spacedapart from the center of said deflection magnetic field along thedirection perpendicular to the direction of said deflection magneticfield.
 6. An image transferring apparatus according to claim 5, whereinsaid projection lens has a plurality of magnetic poles and saiddeflection coil and said correction coils are disposed on the inside ofthe magnetic pole of said projection lens positioned nearest to saidmask.